1. Field of the Invention
The present invention relates to flow testing apparatus and more particularly pertains to a new flow testing system for fluid networks that permits conducting flow testing of a hydrant on the water supply system by a single person in a highly automated and accurate manner.
2. Description of the Prior Art
Fluid supply networks, such as municipal water supply systems, typically test the flow and pressure characteristics of outlets, such as hydrants, on the system to determine the capabilities of the system to deliver an adequate flow of water during high water use events such as the fighting of a fire using water from the supply system.
Not only are these characteristics of the municipal water supply system a concern of the municipality in gauging the likely ability of the fire department to fight fires, but insurers of property are also concerned with this capacity in setting insurance rates for the property. Accurate and current data for each hydrant indicates how much water is available from each hydrant, which may affect fire suppression practices at different points on the system so as not to place greater fire fighting water demands on the hydrant than the individual hydrant or hydrants can supply. The hydrant flow characteristics are not measured in isolation from other proximate hydrants, so that fire fighting personnel are aware whether the system will support the use of multiple proximate hydrants without simply diverting the flow from hydrants already opened and being utilized. Additionally, the use of fire fighting equipment to draw water from the hydrant using a pump can increase the flow capacity of water from the water supply system, but attempting to pump water from the hydrant in excess of the safe capacity of water available from the hydrant at that point in the supply system can have effects detrimental to the system due to the creation of a negative pressure condition created in the main. These detrimental effects include triggering a collapse of the water main or the introduction of contaminants into the main through cracks or joints in the pipe. Thus, knowledge of the actual flow capabilities of the water supply system at a hydrant is needed as guidance to fire fighting personnel seeking to draw water from the hydrant in emergencies.
Similarly, in an actual firefighting situation, it is desirable to monitor the residual pressure in the water supply system as water is being pumped or drawn out of the supply system by fire fighting equipment to ensure that the pressure in the supply system does not fall below a desired threshold pressure and possibly cause the aforementioned problems.
Further, flow test data can provide information for the water supply system for system managers to estimate the capabilities of water mains and plan system upgrades and expansions. Hydrant flow characteristics can affect decisions as to what fire protection and fire resistance features are required for areas of new developments, and where priorities should be placed with respect to upgrading older, smaller water mains. Such testing can indicate systemic weaknesses such as failing water mains and compromised valves.
The testing is typically conducted on a periodic basis, since water supply systems are constantly being affected by changing conditions, including improvements to the system, deterioration of parts of the system, and changes in usage of the system, etc. The testing of hydrants in a water supply system may follow the requirements of National Fire Protection Association (NFPA) No. 291, entitled “First Flow Testing and Marking of Hydrants”. In general, the testing of hydrants in a municipal water supply system involves the measurement of static pressure, residual pressure and pitot pressure with respect to the subject hydrant being tested. However, the procedures of such testing are not performed only at the subject hydrant being tested, but also at another hydrant proximate on the water supply system to the subject hydrant, in order to get an accurate idea of the subject hydrant's individual characteristics and efficiency. More specifically, static pressure and then residual pressure are measured at the subject hydrant, while pitot pressure is measured in a flow of water at a proximate location on the water supply system, such as a fire hydrant adjacent to the subject hydrant being tested on the water supply system (or other access points to the water flow, even from a nearby residential water service). Because the water in the supply system is flowing at the proximate or adjacent hydrant, the measurements taken at the subject hydrant is substantially isolated from effects such as friction loss, and the measurement of these characteristics is thus more accurate.
It will be noted that although the hydrants are proximate or adjacent to each other in the water supply system, the hydrants are typically widely separated in a geographic sense, and personnel are usually stationed at each of the hydrants to conduct the testing.
Just as significant as the physical separation of the subject hydrant and the proximate hydrant is the temporal requirements of the testing. More specifically, while the static pressure is typically measured at the subject hydrant just prior to opening the proximate hydrant to flow water from the system, the measurement of pitot pressure at the proximate hydrant and residual pressure at the subject hydrant must occur simultaneously.
Due to these geographical and temporal requirements of the testing, one person alone is not able to accurately conduct the testing, and at least two persons are required. Thus, the expense of the testing process is increased by the personnel costs. Also, the simultaneous timing of the measurements is not always reliable, as the personnel must communicate the exact time of the taking of the measurement, once the proximate hydrant valve has been fully opened and the pressure in the water main has stabilized. Communication of this timing is thus often performed verbally by the personnel over a portable radio system. Also, there is rarely if ever any independent verification of the simultaneous timing of the taking of these measurements.
Further increasing the expense and complication of the testing are situations where more than one hydrant needs to be opened to achieve a desirable drop in residual pressure approaching 25 percent from the static pressure. This adds to the personnel expense and complication to the timing of the opening of the hydrants.
In the fire-fighting situation, where it is desirable to monitor the pressure in the water supply system, an additional fire fighter or municipal employee must be stationed at a hydrant proximate to the hydrant from which water is being drawn in order to monitor the residual pressure in the supply system. This situation thus also requires additional personnel simply to monitor flow conditions in the supply system.
It is also desirable to coordinate the opening of the proximate hydrant and the taking of pressure and flow readings in order to minimize the time that the flow hydrant is opened, thereby minimize the amount of water that flows from the proximate hydrant, and thereby minimizing the amount of water that is wasted and that needs to be disposed of.
Using the static, pitot, and residual pressure measurements, the flow rate in gallons per minute may be calculated using the formula:Q=29.83 cd2√{square root over (p)}where Q=observed flow, c=coefficient, d=outlet diameter, p=pitot pressure.
The available flow may be calculated, subject to some qualifications, using the formula:
      Q    R    =            Q      F        ×                  h        r        0.54                    h        f        0.54            where Qf=observed flow, hr is the drop in pressure from the static pressure to the desired residual baseline and hf is the drop in psi from static pressure to the actual residual pressure that was measured during the test.
Due to the accuracy required in making the measurements, and the labor intensive nature of the taking of the measurements over sometimes long distances, it is believed that there is needed a system for administering the flow testing and recording the various measurements in a manner that is able to increase the accuracy of and decrease the personnel needed for flow testing of outlets on a water supply system.